Always remember what the purpose of a game is.
In your case - is the goal of the game to explore an area and, as a reward for exploring, sex scenes happen? The sex is adequately described, sure, but the real meat of it is how you get from A to B, not what happens at B.
Or is the goal of the game to fuck a lot, and the world exists just to keep it from literally being sex scene after sex scene after sex scene, to provide a lull in the action, that the trip from A to B exists simply because you don't want the player to read the start of a scene immediately after an orgasm description?
If it's the former - then just... real roughly imagining a public park sort of hunting ground, I'd figure a 4x4 (16 distinct rooms) is too small, but an 8x8 (which is 64 distinct rooms) will provide a better experience - if a little harder to navigate. Add in a few subrooms (area under a bridge, small cave, large hollow tree trunk, etc) and you're done.
If you were doing an entire city, then I'd say twelve or so "neighborhoods" of assorted rooms in a rough 4x5 arrangement branching off from two central intersecting roads of five rooms each should do it. Basically imagine a giant +, with eight neighborhoods on the side of each line, the four in the middle being the same for each line. Here, a shit map with a neighborhood subset. Each intersection'd be a room, the large squares are just signifying the neighborhood areas, the little map showing more or less how one might be arranged.
Gives you a lot of room to move around as a player without it being overwhelmingly complex.
In any case, the biggest issue I've always faced in text adventures, adult or otherwise, is when a room has more than four exits and the point of the game isn't exploration, but doing specific tasks for specific people. Navigation, even when the engine used provides a map, is a pain in the ass just from having to differentiate the separate exits. Especially when it's all a giant grid.
I personally like it when the game has one or more centralized areas - either a room or a 2x2 space - where exits lead off to essentially corridors where you're generally presented with movement options of "Keep Going | Explore the new thing | Go back" - where a corridor will extend for, say, 6 rooms and each one of those six rooms has one room branching from it, which deadends.
It seems to help the player remember where things are without also requiring fifteen minutes of n n n n n n n n n w n n n n n n w n n n e n n w n n e s e n n.
But - that's assuming the purpose of the game isn't exploration, but the interactions.
